That's one theory. Here's a more plausible one. We entered to the war on the Western front to relieve the pressure Hitler was putting on Russia on the Eastern front. This was the result of Roosevelt's socialist, pro-Russian leanings and his desire to keep Russia from total annihilation. If we had held off, the Germans and Russians would have beaten each other into the dust and we could have then swept things up. Instead, we had to fight Germany and ended up with a 50-year Cold War. Remember, Roosevelt deliberately provoked Pearl Harbor. See WORLD WAR II: The Rest of the Story by Richard J. Maybury for more info along this line.
This is probably correct.
Look at what Roosevelt did with Torch. He kept Vichy in power rather then using the Free french.
It's more focused on the internal politics of the US, but goes into some detail regarding FDR and "unconditional surrender". Apparently, Churchill wasn't even consulted prior to FDR blurting it out at Casablanca.